Basic changes to allow loading of local model files (#59)

-modify main,py to not hardcode using DEFAULT_VARIANT

-allow submission of path string to path of variant.yaml file saved in
custom directory in lieu of model variant identifier in CLI to use when
loading model

-addresses #57

tests/test_cli_generate.py

@@ -76,7 +76,7 @@ def test_generate_with_custom_parameters(tmp_path):
             "generate",
             "--text",
             "Testing custom parameters.",
-            "--variant",
+            "--config",
             DEFAULT_VARIANT,
             "--temperature",
             "0.8",